Premium Supporter

In the meantime, you could backup your stuff to external media first, and then do a W10 Clean Install and download the latest GPU drivers, as well as the latest Steam version. Retest.

If that doesn't work, you may need to test your hardware, as a failed hard drive or RAM memory chip could be causing spurious results even with known good drivers. This could take 1-3 days depending on capacity or RAM or HDD.

If that's too much trouble, you could simply replace the HDD with a new one of equal or higher capacity and reinstall W10, drivers, Steam. That should fix it.